Process for making cyclobutane-1, 2-dicyanides



United States Patent We 3,275,675

Patented Sept. 27, 1966 3 275 675 the dye, such as the cyclobutanedcyanide itself, may be PROCESS FOR A Z CYCLOBUTANE used in the processof this invention.

LZ-DICYANIDEE; The structure of indigo carmine is as follows:

James D. Idol, .Ir., Shaker Heights, Janice L. Greene,

Warrensville Heights, and Nancy R. Gray, Cleveland, 5 Ohio, assignors toThe Standard Oil Company, Cleveland, Ohio, a corporation of Ohio NoDrawing. Filed Feb. 17, 1964, Ser. No. 345,076 6 3 Claims. (Cl. 260-464)C N MO S- This invention relates to a process for making cyclo- 1O :0butane-1,2-dicyanides from an alpha,beta-olefinioally un- $0 M saturatednitrile such as acrylonitrile. N 0

It has been proposed heretofore to convert acrylonitrile tocyclobutane-1,2-dicyanide by heating the acrylonitrile in the liquidphase. The reaction involved can be represented by the followingequation:

f wherein M is hydrogen or a metal ion and preferably an CC alkali metalion. 4CH2=CHCN NO /1' H/I I H f1 H ft It is surprising that the disodiumsalt of indigo carmine, for instance, functions so well in the instantprocess in l view of the results obtained with Congo red, also a H (3N0N 0N disodium salt of a dye having the structure ITTHZ S0 Na SO Na NH;M

The product is capable of existing in either the cis or Dimerizationreactions of acrylonitrile carried out in the trans geometric isomericform and both forms are propresence of Congo red resulted in the nearlytotal conduced by the foregoing reaction. The isomers may be version ofacrylonitrile to dark polymeric material. readily separated from theirmixtures by eflicient vacuum The process of the present invention isfurther illusdistillation techniques. Similarly, other alha-beta-oletrated in the following example wherein the amounts offinically unsaturated nitriles, such as methacrylonitrile, ingredientsare expressed as parts by weight unless othercan be employed in thepresent process to form addition wise indicated. compounds of two of theunsaturated nitrile moieties. Example The formation of cyclobutanedicyanides from alpha, beta-olefinically unsaturated nitriles having thestructure In Carrying out the Process, acrylonltl'lle Was Placed in astirred autoclave and the inhibitor was added. In some of theexperiments (Tables I and III) a two-liter stainless steel autoclave wasused and 800 grams of i acrylonitrile were charged. The autoclave had agas inlet tube and internal coils by means of which the contents couldbe heated or cooled. In other experiments (Tables wherein R is hydrogenor a lower alkyl radical a specific 11 IV, V, VI and VII) a cc autodavewas used d example of Which is acrylonimle is normally 41000111" 50 20grams of acrylonitrile were charged for each run. Panied y Considerableformation of P l The After the acrylonitrile was charged in theautoclave POIYIHGI' 0ftll interferes With the dlIl'lEllZfltlOl'l processand the autoclave as sealed nitrogen gas was passed by fouling theEquipment, discoloring the Pmduct and through the inlet tube and thecontents of the autoclave generallylowering the yield of the desiredproduct. The were thoroughly purged of Oxygen The inlet tube was Polymer15 y dark in appearance the Poll/men then sealed and the reactor andcontents were brought to Zatlon Probably mvqlvqs a reaction of cyan)groups reaction temperature and maintained at this temperature as Wellpiflynielilzanon through the l as under autogenous pressure withstirring for a desired often occurs in nitrlle polymers when they aresub ected 1e ngth of time The autoclave was then cooled, Opened,

' h e s. to big t mperature and the contents were removed for analysisand the COIldl- We have discovered in accordance with our invention f h1 f f h 1 d that if an alpha,beta-olefinically unsaturated nitrile suchHon 0 t e mterna Sm aces 0 t e autoc'ave was note as acrylonitrile isheated in a liquid or vapor phase, at and rated heremafter descnbed'autogenous or elevated pressures, in the absence of air Contents of thereactor Wfire analyzed chromato or oxygen, and in the presence of smallamounts of indigo graphically and amounts of the reaction Product andCarmine dye, d Conversions to the dimer, cyclobutane unreactedacrylonitrile were determined. The material 1,2-dicyanide, can beobtained Without, or at least with balance based acrylonitfile WeightCharge Versus a minimum of, polymer formation. An additional en- Weightof the Cyclobutane-LZ'diCYaHide P1118 l-lllfeacted hancement is achievedby the addition of small amounts acfylonitrile gave an indication of theamount of undeof water to the reaction mixture. The function of theSifable P y formation Inside the reactor, the Coils water is not readilyapparent but it probably increases and th reaeti n mixture Were examinedvisually and the solubility of the indigo carmine in the reactionmixphotographs of them were taken. On this basis, the

ture. Other liquids which have a solubilizing action on extent ofpolymer formation was rated on a scale of from zero to ten. What wasconsidered to be an unsuccessful run was one in which the nitrilecomponent was converted completely to solid polymer and this was given arating of zero. The rating scale is described in more detail in Table I.This scale is similar to, but not identical with that used for thesmaller autoclave experiments. The ratings for the small reactorexperiments are given in Table II.

A study of the reaction variables is summarized in Tables III to VII.The effect of adding 0.05% by weight of indigo carmine (disodium salt)to the reaction mixture is shown in Table III. The data shows that withindigo carmine present, conversion to the dimer is substantiallyconstant while the polymer formation is considerably decreased. Theaddition of small amounts of water further reduces polymer formation, asshown by the data summarized in Table IV. The results obtained on theaddition of Water and indigo carmine, both separately and concurrentlyto the reaction mixture show that addition of water by itself (inamounts of 3%) results in the predominant conversion of acrylonitrile topolymer, even when added in substantial amounts. Although the additionof indigo carmine by itself greatly reduces polymer formation andincreases dimer yield, further improvement is obtained with the combineduse of 0.05% indigo carmine and 3% water.

The formation of polymer in the reactor is highly undesirable because itinvolves lengthy cleanup periods, and also the overall conversion ofnitrile component to the desired addition product is decreased withincreasing amounts of polymer formed.

The amount of inhibitor employed may vary from 0.01 to about 1.0% byweight based on the acrylonitrile charged. Generally, the preferredrange is about 0.05 to 0.5% by weight. If water is employed, amountsranging from 1% to 20% of water by weight based on acrylonitrile chargedmay be utilized. (Table IV.)

A study of the dimerization reaction in the vapor phase is shown inTable VI. The reaction mixture contained only indigo carmine inhibitorin amounts of 0.1% by weight. The experiments were conducted at lowacrylonitrile pressures and therefore conversions were expected to below. This effect is substantiated by data in Table I of British PatentNo. 897,275 which shows that conversions to the dimer are increased withincreased pressures. The data in Table VI show that though the yields ofdimer were low, the indigo carmine successfully inhibited acrylonitrilepolymerization for residence times of 0.25 to 1.0 hour at temperaturesin the 265278 C.

range.

The effect of adding acrylonitrile dimer as a solvent in the vapor phasedimerization reaction is shown by the data in Table VII. The polymerratings were improved where the acrylonitrile dimer was present at thebeginning of the reaction.

The temperature of the reaction should be fairly high in order toachieve reasonable yields in a reasonable time. The minimum practicaltemperature is in the range of 175 to 200 C. and the maximum about 350C. where the formation of by-products usually becomes excessive.

The reaction time or the reactor residence time exents an effect on theamount of acrylonitrile monomer which can be converted to the dimerbefore excessive polymerization sets in. Generally, it has been foundthat to keep polymer formation at a minimum, shorter reaction timesshould be employed. Reaction times of from A to about 7 hours may beemployed, depending upon the reaction temperature used.

Methacrylonitrile was substituted for acrylonitrile in the foregoingprocedure with similar results. Similarly, mixtures of acrylonitrile andmethacrylonitrile in various proportions may be employed in the processof the present invention,

TABLE I [Reaction temperature: 240 C. Reaction time: 3 hours] Darkbrown-bcgins to be rather viscous. Dark brownviscous Very thick blackgoo nearly solid, low dimer conversion.

coils, sides, bottom, loose polymer.

Much polymer (coils may be stuc Much polymer (coils probably stuck).

All solid TABLE II [Reaction temperature: 240 C. Reaction time: 4 hours]Rating Liquid Product Appearance Autoclave Appearance 10 Clear,colorless or almost N o polymer.

colorless.

9 Yellow-1nay contain some Trace of polymer.

polymer sediment.

8 Yellow-orange, may con- Slightly more than trace of tain some polymersedipolymer. ment.

7 Yellou brown, probably Very thin i polymer contains polymer sedibuildup in bottom, may mcnt. have polymer film on sides.

6 Yellowbrown, polymer Thin layer An) polymer sediment. build up inbottom, may

have polymer film on sides.

Orange-brown, polymer Layer of polymer (-X sediment. on bottom, probablypolymer film on sides.

4 Brown-polymer scdiment polymer in bottom probably polymer film.

3 Brown liquid, may or may g. polymer.

not be viscous.

2 Brown-viscous polymer, Much polymer.

low dimer conversion.

1 Very thick, nearly solid product.

0 All solid polymer, NH;

odor.

TABLE III Time, Dimer Material Polymer Indigo Carmine Hours Conver-Balance Rating sion None 3 18. 1 89. 5 4

0.05%+2.5% HzO 3 15.1 96 9. 5

Conditions:

Nitrogen Purge, Minutes. Temperature, 240 0.

TABLE IV Additive Dimer Polymer Conversion Rating 0.05% Indigo Carmine14. 9 7

0.10% Indigo Carmine 12. 5 7

0.05% Indigo Carmine 3% H20 18.6 9

0.05% Congo Red 0 0 Conditions:

Temper Time, 4

ature, 240 0. hours.

TABLE V Weight Percent Dimer Polymer Indigo Conversion Rating CarmineConditions:

Nitrogen Purge, 3 Minutes. Temperature, 240 C. Time, 4 Hours.

TABLE VI Tempera- Time, Dimer Polymer ture, 0. Hours Conversion RatingConditions:

Reactor Charge, 20 g. aerylonitrile plus 0.02 g. Indigo Carmine.

Nitrogen Purge, 3 Minutes.

1 Temperature, Autoelaveswere placed in aheated aluminum stirring blockat a temperature of 275 C. Within 5 minutes the temperatures had fallento 240 C. and then rose to the temperatures noted in the above table.

+ 53.7% aerylonitrile +01% Indigo Carmine.

Conditions:

Nitrogen Purge, 3 Minutes. Temperature, 275 C.

It is to be understood that any of the conventional techniques inoperating autoclaves and. in working up the products may be employed asis obvious to one skilled in the art without departing from the scope ofthe present invention which is limited only by the appended claims.

We claim:

1. The process of forming a cyclobutane-l,2-dicyanide which comprisesheating for from A to about 7 hours at least one nitrile selected fromthe group consisting of acrylonitrile and methacrylonitrile to atemperature of from to 350 C. in the substantial absence of molecularoxygen and in the presence of from 0.01 to about 1.0% by weight ofindigo carmine dye having the structure wherein M is selected from thegroup consisting of hydrogen and an alkali metal.

2. The process of claim 1 wherein the niononitrile is acrylonitrile.

3. The process of claim 2 wherein from 1 to 20% by weight of Water isalso employed.

No references cited.

CHARLES B. PARKER, Primary Examiner.

JOSEPH P. BRUST, Assistant Examiner.

1. THE PROCESS OF FORMING A CYCLOBUTANE-1,2-DICYANIDE WHICH COMPRISESHEATING FOR FROM 1/4 TO ABOUT 7 HOURS AT LEAST ONE NITRILE SELECTED FRMTHE GROUP CONSISTING OF ACRYLONITRILE AND METHACRYLONITRILE TO ATEMPERATURE OF FROM 175 TO 350*C. IN THE SUBSTANTIAL ABSENCE OFMOLECULAR OXYGEN AND IN THE PRESENCE OF FRM 0.01 TO ABOUT 1.0% BY WEIGHTOF INDIGO CARMINE DYE HAVING THE STRUCTURE